Claims:
1. A suspension system (100) for engaging and disengaging a lift axle (106), the suspension system (100) comprising:
a master axle (104) operatively connected to a chassis frame (102) via an airbag (108), wherein the master axle (104) comprises a first arm (114) and a second arm (116), and wherein the second arm (116) comprises a pivot point (118); and
a lift axle (106) mounted on the second arm (116) at the pivot point (118), wherein one end of the lift axle (106) is displaced between the first arm (114) and the second arm (116), wherein the one end is coupled to the first arm (114) via a first spring and damper assembly (110) on one side, wherein the one end is coupled to the second arm (116) via a second spring and damper assembly (112) on opposite side,
wherein during operation, the lift axle (106) is configured to move in one of an upward direction or a downward direction based on a payload on the chassis frame (102) thereby engaging and disengaging the lift axle (106).

2. The suspension system (100) as claimed in claim 1, wherein during engaging when the payload is increased beyond a predetermined threshold limit, the master axle (104) moves in the upward direction in turn pushing the lift axel (106) in the downward direction based on compression of the airbag (108) and the first spring and damper assembly (110).

3. The suspension system (100) as claimed in claim 1, wherein during disengaging when the payload is decreased below a predetermined threshold limit, the master axle (104) moves in the downward direction in turn pushing the lift axel (106) in the upward direction based on loosening of the airbag (108) and the second spring and damper assembly (112).

4. The suspension system (100) as claimed in claim 1, wherein the master axle (104) is coupled to a rear wheel and the lift axle (106) is coupled to a slave wheel at the other end.

5. The suspension system (100) as claimed in claim 4, wherein the slave wheel is displaced between the rear wheel and a front wheel of a vehicle.

6. The suspension system (100) as claimed in claim 1, wherein the master axle (104) comprises a seat (120) positioned adjacent to the first arm (114) and above the rear wheel.

7. The suspension system (100) as claimed in claim 6, wherein the seat (120) is configured to house the airbag (108) between the chassis frame (102) and the master axle (104).

8. The suspension system (100) as claimed in claim 1, wherein the airbag (108) is a bellow.
, Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of invention:
LOAD BASED TANDEM SUSPENSION SYSTEM

Applicant:
Tata Motors Limited
A company Incorporated in India under the Companies Act, 1956
Having address:
Bombay House, 24 Homi Mody Street,
Hutatma Chowk, Mumbai 400001,
Maharashtra, India

The following specification describes the invention and the manner in which it is to be performed.

PRIORITY INFORMATION AND DEFINITIVE STATEMENT
[001] This patent application does not claim priority from any application.

TECHNICAL FIELD
[002] The present subject matter described herein, in general, relates to suspension system in heavy commercial vehicles and more particularly to a suspension system for engaging and disengaging a lift axle based on a payload on a chassis frame.

BACKGROUND
[003] Generally, heavy commercial vehicles are used to transport tons of payload from one place to other. It has been observed that the vehicles may also be overloaded with the payload. However, a load bearing capacity of each wheel is also limited. Thus, overloading the vehicle with the payload results in increased weight of the vehicle thereby degrading performance of the vehicle. In order to overcome the aforementioned problem, the conventional systems and methodologies have been developed to provide an auxiliary wheel along with a rear wheel to support the overloaded vehicle. However, the auxiliary wheel increases overall frictional force exerting on the vehicle thereby reducing the performance of the vehicle.

SUMMARY
[004] Before the present systems are described, it is to be understood that this application is not limited to the particular systems, and methodologies described, as there can be multiple possible embodiments which are not expressly illustrated in the present disclosure. It is also to be understood that the terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope of the present application. This summary is provided to introduce concepts related to a suspension system for engaging and disengaging a lift axle and the concepts are further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.
[005] In an implementation, a suspension system for engaging and disengaging a lift axle is disclosed. The suspension system may comprise a master axle, a lift axel, a first spring and damper assembly, a second spring and damper assembly, an airbag, and a chassis frame. The master axle may be operatively connected to a chassis frame via an airbag. The master axle may comprise a first arm and a second arm. In one aspect, the second arm may comprise a pivot point. The lift axle may be mounted on the second arm at the pivot point. It is to be noted that one end of the lift axle may be displaced between the first arm and the second arm. The one end may be coupled to the first arm via the first spring and damper assembly on one side. The one end may be coupled to the second arm via the second spring and damper assembly on opposite side. During operation the lift axle may be configured to move in one of an upward direction or a downward direction based on a payload on the chassis frame thereby engaging and disengaging the lift axle.

BRIEF DESCRIPTION OF THE DRAWINGS
[006] The foregoing detailed description of embodiments is better understood when read in conjunction with the appended drawing. For the purpose of illustrating the disclosure, example constructions of the disclosure are shown in the present document; however, the disclosure is not limited to the specific apparatus disclosed in the document and the drawing.
[007] The detailed description is given with reference to the accompanying figure. In the figure, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawing to refer like features and components.
[008] Figure 1 illustrates a system for engaging and disengaging a lift axle, in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION
[009] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "coupled," "mounted," "pivoted," "connected," “holding”, “house”, “engaging”, “disengaging” and other forms thereof, are intended to be open ended. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although a suspension system for engaging and disengaging a lift axle, or similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.
[0010] Various modifications to the embodiments will be readily apparent to those skilled in the art and the generic principles herein may be applied to other constructions of the system for providing stiffness to a vehicle. However, one of ordinary skill in the art will readily recognize that the present disclosure of the suspension system for engaging and disengaging a lift axle is not intended to be limited to the embodiments illustrated, but is to be accorded the widest scope consistent with the principles and features described herein. It should be appreciated by the one of ordinary skill in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure.
[0011] The present subject matter describes a suspension system for engaging and disengaging a lift axle in a heavy commercial vehicle. The suspension system comprises a master axel, an airbag, a first spring and damper assembly, and a second spring and damper assembly. It is to be noted that the master axle and the lift axle are further connected to a rear wheel and a slave wheel respectively. The slave wheel is an auxiliary wheel which is engaged only when the payload limit on the rear wheel exceeds the predetermined threshold limit. In addition, the slave wheel is disengaged when the payload limit on the rear wheel decreases below the predetermined threshold limit. It is to be noted that the suspension system facilitates a load sharing between the rear wheel and the slave wheel based on the payload on the chassis frame.
[0012] It is important to note that the present system is advantageous over the conventional systems as the present system automatically engages the slave wheel based on variations in the payload. It may also be noted that the present system enables engaging and disengaging of the slave wheel in real time when a vehicle is in motion. While aspects of described system and method for engaging and disengaging a lift axle and may be implemented in any number of different structures, components, and/or constructions, the embodiments are described in the context of the following exemplary system.
[0013] Referring now to Figure 1, a suspension system 100 for engaging and disengaging a lift axle of a vehicle, in accordance with an embodiment of the present subject matter is disclosed. The suspension system 100 comprises a master axle 104, a lift axel 106, a first spring and damper assembly 110, a second spring and damper assembly 112, an airbag 108, and a chassis frame 102. It is to be noted that the master axle may be configured to bear a payload equivalent to a predetermined threshold limit. The master axle 104 may be operatively connected to the chassis frame 102 via the airbag 108 at one end. The master axle 104 may comprise a first arm 114 and a second arm 116. The master axle may be a substantially “U” shaped component with the first arm 114 and the second arm 116 representing arms of the substantial “U” shape. In one aspect, the second arm 116 may comprise a pivot point 118. The master axle 104 may further be coupled to a rear wheel at other end. The master axle 104 may comprise a seat 120 positioned adjacent to the first arm 114 and above the rear wheel (not shown). The seat 120 may be configured to house the airbag 108 between the chassis frame 102 and the master axle 104. The airbag 108 may be a bellow.
[0014] The lift axle 106 may be mounted on the second arm 116 at the pivot point 118. It is to be noted that one end of the lift axle may be displaced between the first arm 114 and the second arm 116. Further, the lift axle 106 may be coupled to a slave wheel (not shown) at another end to share the payload. The slave wheel may be displaced between the rear wheel and a front wheel of the vehicle. It is to be noted that the slave wheel may be configured to share the payload of the rear wheel. In one embodiment, the slave wheel may be configured to bear the payload equivalent to the rear wheel. In another embodiment, the suspension system 100 may comprise a plurality of the lift axle to share the increased payload on the chassis frame 102.
[0015] In addition, the one end of the lift axle 106 may be coupled to the first arm 114 via the first spring and damper assembly 110 on one side. The one end may further be coupled to the second arm 116 via the second spring and damper assembly 112 on opposite side. The first spring and damper assembly 110 and the second spring and damper assembly 112 may function as a shock absorber. The first spring and damper assembly 110 and the second spring and damper assembly 112 may comprise at least one spring and one damper to maintain equilibrium between the master axle 104 and the lift axle 106. Example of the spring may include, but not limited to, a helical compression spring, a helical extension spring, a conical spring, a laminated or leaf spring, a torsion spring, a disc or a Belleville spring. Types of the damper may include, but not limited to, a metallic damper, a viscoelastic damper, and a frictional damper.
[0016] During operation, the lift axle 106 may be configured to move in one of an upward direction or a downward direction based on a payload on the chassis frame 102 thereby engaging and disengaging the lift axle 106. In one embodiment, during engaging when the payload is increased beyond a predetermined threshold limit, the air bag 108 is compressed because of increment in the payload leading to movement of the master axle 104 in the upward direction. Further, the spring present in the first spring and damper assembly 110 is compressed and the spring present in the second spring and damper assembly 112 is tensioned. Thus, in order to maintain the equilibrium, the first spring and damper assembly 110 pushes the lift axel 106 in the downward direction thereby engaging the slave wheel for sharing the payload with the rear wheel.
[0017] In another embodiment, during disengaging when the payload is below a predetermined threshold limit, the air bag 108 is loosened because of decrease in the payload leading to movement of the master axle 104 in the downward direction. Further, the spring present in the first spring and damper assembly 110 is tensioned and the spring present in the second spring and damper assembly 112 is compressed. Thus, in order to maintain the equilibrium, the second spring and damper assembly 112 pushes the lift axel 106 in the downward direction thereby disengaging the slave wheel for sharing the payload with the rear wheel.
[0018] In order to elucidate the functioning of the aforementioned system, consider an example of a vehicle with a suspension system in accordance with an embodiment of the subject matter. Assuming the predetermined threshold limit for carrying payload of the rear wheel is ‘10 tons’. Thus, when the payload increases to ‘20 tons’ performance of the vehicle is significantly reduced. In current scenario, when the payload increases to ‘20 tons’, the master axel moves in the upward direction because of compression of the airbag. Once the air bag is compressed, the first spring and damper assembly automatically pushes the lift axle in the downward direction thereby engaging the lift axle. The lift axle may share an increased payload of ‘10 tons’ with the master axle. It is to be noted that the slave wheel, connected to the lift axle, may be configured to bear the increased payload of ‘10 tons’ with the rear wheel.
[0019] In another example, when the payload of ’20 tons’ is reduced to ’10 tons’, the airbag may be automatically loosened pushing the master axle in the downward direction. Once the master axle is pushed to the downward direction, the spring present in the second spring and damper assembly may be compressed in turn pulling the lift axle in the upward direction thereby disengaging the lift axel. It is to be noted that disengaging the lift axle is advantageous in improving performance of the vehicle. In one aspect, disengaging the lift axle reduces a frictional force being exerted on the vehicle.
[0020] Exemplary embodiments discussed above may provide certain advantages. Though not required to practice aspects of the disclosure, these advantages may include those provided by the following features.
[0021] Some embodiments enable a suspension system to engage and disengage a lift axle based on a payload on a chassis frame of a vehicle.
[0022] Some embodiments enable a suspension system to reduce the frictional force exerting on the slave wheel when the payload is below a predetermined threshold limit.
[0023] Some embodiments enable a suspension system to automatically engage and disengage a lift axle in real time based on the payload.
[0024] Some embodiments enable a system to modify the predetermined threshold limit based on load bearing capacity of rear wheel and slave wheel.
[0025] Some embodiments enable a suspension system to improve performance of the vehicle.
[0026] Some embodiments enable a suspension system to improve load bearing capacity of the vehicle.
[0027] Although implementations for a suspension system to engage and disengage a lift axle of a vehicle have been described in a language specific to structural features and/or methods, it is to be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as examples of implementations for a suspension system to engage and disengage a lift axle.